M7350 has no DDNS feature according to the user guide. MR3040 should be more proper for you.

Lights are normal indeed. It seems that there is an annoying frozen issue. Get a replacement to test under warranty.

Maybe you should test the speed in different ways to compare it. Read #7 and #8. http://forum.tp-link.com/showthread.php?78570-TD-W9980-slow-broadband-speed-with-talktalk&region=china

Hardware version of your W8960N? http://www.tp-link.com/en/products/details/?categoryid=&model=TD-W8960N#down If there is a newer firmware, upgrade it and reconfigure it. If not, if it works for...

That's normal...It means that maximum number of clients supported is 8.

Umm, it is strange. Can you try a different PC?